She doesn't fire in "The Battle", but in "Peak Performance". It's fortunate that the distant shot from that episode is essentially the only one to ever reveal the underside of the model on screen, so we don't learn the sad truth:

As for the torpedo launchers, those were never actually painted in or lit. The torp decks of the Constitution neck piece were simply installed as is but left unpainted - just like the blue domes in the Constitution impulse engine pieces were left unlit. But supposedly there are twin launchers at both the top and the bottom pylon, giving the total of four. Good shots of them don't exist, alas.

The desktop model does nicely show where the top pair would go, though. This allows us to spot it in the Stargazer onscreen bow view as well, despite the lack of illumination.

Might be these aren't torp launchers, of course. But the ship has those somewhere, as per dialogue from "The Battle". It would be a bit clumsy to claim that an all-new fixture (such as the odd barrel on the underside) is a torpedo launcher if also simultaneously claiming that these familiar features are not.